Bioavailability and pharmacokinetics of carbon-14-cyproterone acetate-methylene (2 mg) and tritiated ethinyl estradiol (50 mg) after oral administration as a coated tablet (SH B 209 AB) were investigated. 8 women received the compounds and carbon-14 and tritium activity in plasma urine and feces was determined up to 7 or 10 days postadministration. Cyproterone acetate was completely absorbed. The maximum plasma level was reached in 30 minutes to 3 hours when 2.2% of the dose was found in total plasma corresponding to 24 ng eq/ml. The plasma level decreased with a 1/2-life of 7.9 hours (distribution and elimination) and later with a 1/2-life of 2.5 days (elimination). Elimination via urine was 37% and up to Day 10 postadministration 91% of the dose was found in urine and feces. Ethinyl estradiol was adsorbed very rapidly and almost completely with the maximum plasma level reached in 60 minutes. At this time 10% of the dose was found in the plasma corresponding to 2.1 ng eq/ml. The plasma level dropped up to about 8 hours postadministration with a 1/2-life of 5.1 hours and later with a 1/2-life of 27 hours. Ethinyl estradiol was eliminated in urine and feces in the ratio of 4:6 and 91% of the dose was recovered.